Brake boosters of the type in question are sufficiently well known. In this case, a connection of the working chamber to atmosphere is opened by the control valve during a braking operation. As a result, a pressure difference builds up between the working chamber and the vacuum chamber, and the control housing is displaced in the direction of the vacuum chamber together with the movable wall. On completion of a braking operation, an air connection between the working chamber and the vacuum chamber is opened by the control valve, a process involving the unblocking of the extraction duct by the control valve. During this process, the control housing travels back in the direction of the working chamber together with the movable wall.
Because drive motor noises and other secondary noises are less and less perceptible in well insulated interiors of modern motor vehicles, the noise produced by many pneumatic brake boosters, which are generally in circulatory communication with the vehicle interior, is increasingly becoming a central concern and is generally regarded as disadvantageous. Noises which arise during the return of the control housing are often felt to be particularly troublesome, this state of affairs being more or less pronounced in different vehicle applications.